High speed binary counter



July 5, 1960 D. LACY 2,944,224

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2,944,224 Patented July 5, 1960 2,944,224 HIGHSPEED BINARY CDUN'IER Peter D. Lacy, Redwood City, Calif., assignor to Hewlett- Packard Co., Palo Alto, Calif., a corporation of California Filed May 10, 1957, SenNo. 658,337

12 Claims. (Cl. 331-82) This invention relates generally to a high speed binary counter and more particularly to a high speed binary counter making use of a bistable oscillator.

Advances in the fields of nuclear studies and high speed dig-ital computers have created a demand for high speed counters capable of counting random phenomena sep .arated in time by a few millimicroseconds.

It is essential in the counting of random phenomena that the counter havememory, accuracy and speed of :an electron beam with switching from one mode to another being controlled by the excitation of the electron beam.

It is a further object of the present invention to provide a high speed binary counter which employs an oscillator including a helical transmission line coupled to an electron beam, the oscillator being adapted to oscillate at predetermined modes and having. the .helicalytnansmission line coupled to an electron beam. The excitation of the electron beam serves to control the oscillatory mode.

It is a further object of the present invention to provide a high speed binary counter which employs a tube of the traveling wave type having a plurality of sections with one of said sections forming a bistableoscillator.

It is a further object of the present invention to provide a high speed binary counter which employs a traveling wave tube having a plurality of sections, said tube including a section which is adapted to oscillate on predetermined modes coupled to the electron beam and a'front section serving to introduce a switching signal ontothe electron beam whereby the same is excited to effect control of the mode of oscillations of the oscillator section.

These and other objects of the invention will become more apparent from the followingdescription read in conjunction with the accompanying drawing.

Referring to the drawing:

Figure 1 shows one embodiment of my invention;

Figure 2 shows a means for forming a suitable signal for exciting the beam prior .to entry into the bistable oscillator;

a high speed bistable oscillator.

The beam is formed and projected by the combination of the heater 17, cathode 1'8 and plate 19. See for example Pierce, Travelling Wave Tubes, D. VanNostrand C0,, 1950.

As is well known, electromagnetic waves are propagated along a helical transmission line at less than free space velocity. The velocity along the axis of the helical transmission line depends upon the radius and pitch of the helix and is generallymuch less than the free space velocity. When the electron beam velocity is correctly adjusted so that it coincides with the phase velocity of the wave carried by the helix, the two are in synchronism. Under these conditions, there is coupling between the fields of the .beam and those on the helix and the alternating current waves on the beam and the helix grow at the expense of D.-C. beam energy. The wave carried by the helix is amplified as a result of the interaction.

coupler is described in copending application entitled Helix Directional Coupler, Serial No. 403,172, filed January 11, 1954, now abandoned.

In Figure 1, the switching signal which serves to control the degree and nature of beam saturation (the excita- :tion) entering the oscillatory portion of the counter is coupled onto the section of helical transmission line 13 by means of the contrawound directional coupler 21. The section of the tube designated generally by the bracket22 comprises an amplifier section which serves to amplify ,the applied control signal and to modulate or excite the beam in accordance therewith. The bistable oscillatory circuit is formed by the short section of helical transmission line .14 and the line 23 which interconnects the ends of the transmission line. The portion of the tube designated generally by the bracket Ztforms The helical transmission 14 is coupled to the electron beam and waves are excited thereon by the coupling between the waves on the beam and the helix. The waves induced on the helix 14 are coupled to the beam whereby they further excite or modulate the beam in accordance therewith.

By controlling the delay in the feedback in the portion 24, oscillations having the desired mode frequency sep aration A may be obtained. The prevailing relationship for the mode separation is Af=l/ T where T is the time delay in the feedback path. As the delay T is reduced, cf the frequency separation is increased. If the available bandwidth is B, then the theoretical number of modes available is determined by the bandwidth B. Preferably,

in operation the oscillatory modes are spaced as much'as possible in frequency.

The helical portion of the oscillator section serves to modulate the beam traveling therethrough, as previously described. An indication of the mode of oscillation of thebistable circuit maybe obtained by coupling a signal 15 may be coupled oif by means bf a directional coupler 25. The output is then applied to a filter 26 which serves been excited or modulated in' to filter out all components except the desired modes, as

will be presently described. An output signal may also be obtained by introducing a resistor in series with the collector and coupling off the high frequency voltage appearing across the resistor. The section of the tube designated generally by the bracket 24.forms the output section of the electron tube.

For purposes of discussion, assume that the oscillator portion of the binary counter, including the transmission line 14 and feedback path 23, is adapted to oscillate at two distinct frequencies separated by the frequency A The frequencies may be designated as f,, and f The loop gain is adjusted so that the oscillator can only oscillate at one or the other of the frequencies f,, or f but not both frequencies, the bistable condition. I

As previously described, by properly adjusting the degreev and nature lOf beam saturation (excitation) upon entry into the oscillator portion, the loop gain in the bistable oscillator is controllable to effect switching from one oscillatory mode to the other. For example, if the beam is modulated by an appropriate signal in the forward gain section 22, the beam will have the requisite degree and nature of saturation on entry into the oscillatory loop 14.

Fundamentally, the switching from one oscillatory,

gain to be reduced to a value below unity. The desired mode is excited by a signal of appropriate frequency having a magnitude which is greater than that of the remaining undesired mode frequency. By properly modulating (exciting) the beam upon entry into the helical transmission line 14, forming a part of the bistable circuit,

heterodyning of the oscillating mode with the frequency on the beam produces signal components of various types.

'If the frequencies and amplitudes are properly adjusted,

the heterodyning, or non-linear mixing, will produce signal components at the operating frequency of the bistable oscillator which serve to reduce the loop gain in the oscillating mode to a value below one and allow signal components to build up in the other desired mode. Thus, if .the oscillator is operating at the frequentcy f,,, the signal components will reduces the gain at frequency f below. a

. one and excite the frequency f When the signal applied to the forward gain section is removed, the oscillator will then continue to oscillate at the frequencyf By appropriately choosing the signal applied to the forward gain section, a reverse process can becarried out with an identical applied switching signal. Thus, upon excitation'of the beam by application of a second pulse to the forward gain section, the loop gain along the curve II is obtained for f or f weak and f or f strong,-respectively. a

- bistable oscillator. second directional coupler 56.

mode 1, or f whichever is present, from curve I to curve II. The period of the pulse 34 should be approximately equal to the loop delay whereby the heterodyning takes place and the other mode is generated before the pulse is terminated. If the period is much less or much longer than this, switching will not be reliably effected.

Other types of switching signals are suitable for performing the switching. Thus, suppressed carrier phase modulation may be employed. A suitable signal generator 41, Figure 2, generates a continuous wave of frequency f,, and applies the same to the phase modulator 42. The modulator 42 is square wave modulated. The .output of the phase modulator is a suppressed carrier signal having frequency components of the type shown at 43, that is, f in(f f The suppressed carrier phase modulator may be modulated by a single square wave of the type shown at 44 which has sufficient amplitude to vary the phase through 11' radians and a period T which is approximately equal to the loop delay.

The output from the phase modulator of Figure 2 may be applied to an amplitude modulator which is then modulated by a signal of the character shown at 46. This serves to form an output signal which has a single pair of side bands H id -1%)] as shown at 47.

Any of the signals described when employed to-excite an electron beam traveling through the helical portion of the bistable oscillator will serve to switch the bistable oscillator from one mode to another. The latter signals employ diflerence frequencies to switch while the former employs the same frequency.

The bistable oscillator may be formed in a manner other than that illustrated in Figure 1. Referring to Figure 5, for example, the signal is shown applied to the forward gain section by means of a waveguide coupler 51. A pair of contrawound helical couplers 52 and 53 are coupled to a portion of the helical transmission line and include a feedback path 54. The couplers form the An output signal is obtained 'by a The essential feature is that a bistable oscillator be formed which is coupled to an electron beam and which is adapted to oscillate at predetermined mode frequencies separated by a frequency A The oscillator should be responsive to beam excitation whereby one or the other for frequency f will be reduced below one and the freof the modes may be excited. V q

The output signal may be applied to a filter having suitable pass characteristics. For example, assume that f is less than f then when the oscillator is operating on the mode frequency f the output signal will have frequency components f iU -l-f and 2f +f When opcrating at the mode frequency f the output will have the frequency component 11-1-273 Other frequencies will appear but will have such small amplitudes that they may be disregarded in this analysis. If a high pass filter which will pass a frequency 3+2 but will 'reject 2f +f is used, an output signal will be'present at the filter when the bistable oscillator is switched from h,

7 to f,, but not when'switched from f to f Thus division by two is performed by the circuit. For each -A suitable switching signal'for application to the fortwo input pulses a single output pulse is obtained.

Iclaim: 1. A high speed binary counter comprising means forming an electron beam and means serving. to receive said beam, 9. bistable oscillator coupled to said beam and j adapted to o-scillate at predetermined modes said oscillator adapted to oscillate at only one mode at one time, means for exciting the electron beam prior to coupling to the bistable oscillator to switch the oscillator from one oscillatory mode to another.

2. A high speed binary counter comprising a traveling wave tube having means forming an electron beam and means serving to receive the same, a bistable oscillator including a helical transmission line coupled to said beam and adapted to oscillate at predetermined modes, said oscillator adapted to oscillate at only one mode at one time, means for exciting the electron beam prior to coupling to the oscillator to switch from one oscillatory mode to another.

3. A high speed binary counter comprising a traveling wave tube having means forming an electron beam and means serving to receive the beam, an oscillatory loop coupled to said beam and adapted to oscillate at predetermined modes, said loop being adapted to oscillate at only one mode at one time, and means for modulating the electron beam prior to coupling with the loop to switch the oscillatory loop from one mode of oscillation to another.

'4. Apparatus as in claim 3 wherein said means for modulating the beam comprises a slow wave structure coupled to said beam and serving to receive and amplify an input signal and modulate the electron beam in accordance therewith.

5. A high speed binary counter comprising a traveling wave tube having means forming an electron beam and means serving to receive said beam, a first gain section coupled to said beam and adapted to receive an input signal, a second section coupled to said beam and connected to form an oscillator adapted to oscillate at predetermined mode frequencies, said oscillator adapted to oscillate at only one mode at one time, means for applying a switching signal to said first gain section whereby the electron beam is modulated prior to coupling with said second section, said modulation serving to control the grain of the second section to switch the section from one oscillatory mode to another in response to the input signal.

6 A high speed binary counter comprising a traveling wave tube having means forming an electron beam and means serving to receive said beam, a first gain section coupled to said beam and adapted to receive an input signal and excite the beam in accordance therewith, a second section coupled to said beam and connected to form a bistable oscillator adapted to oscillate at the frequencies f or f but not both, means for forming a switching signal having frequency components and 1%,, means for applying said signal to the first gain section to modulate the beam in accordance therewith, said modulated beam serving to control the gain of the second section to switch the frequency of oscillation from one frequency to the other.

7. Apparatus as in claim 6 wherein said switching signal comprises a pulse having a carrier frequency f -l-f 8. Apparatus as in claim 6 wherein said switching signal is a suppressed carrier phase modulated signal having the frequency characteristics f i-n(f,,+f where n is an integer.

9. Apparatus as in claim 6 wherein said switching signal has the frequency characteristics f (f,,+f

10. A high speed binary counter comprising a traveling wave tube having means forming an electron beam and means serving to receive said beam, a bistable oscillator section coupled to said beam and adapted to oscillate at predetermined mode frequencies, means for exciting said beam prior to entry into said bistable oscillator section, means forming a switching signal for application to said last named means, and means for coupling an output signal from said beam after its passage through the bistable oscillator.

11. Apparatus as in claim 10 together with filtermeans connected to receive the output signal and pass predetermined frequencies whereby the oscillating mode of the bistable oscillator may be sensed.

12. A high speed binary counter of the type adapted to be triggered by input pulses comprising a travelling wave tube having means forming an electron beam and means serving to receive said beam, a first gain section including a slow wave structure coupled to said beam, said gain section serving to receive an input signal and modulate the beam in accordance therewith, a second section including a slow wave structure coupled to said beam and connected to form a bistable oscillator adapted to oscillate at the frequency f, or f but not both, means connected to receive the input pulse and serving to form a switching pulse having frequency components f, and f means for applying said pulse to the first gain section to modulate the beam in accordance therewith, said modulated beam serving to control the gain of the second section to switch the frequency of oscillation from one frequency to the other in response to successive pulses.

References Cited in the file of this patent UNITED STATES PATENTS 2,289,756 Clavier et a1. July 14, 1942 2,425,748 Llewellyn Aug. 19, 1947 2,724,775 Field 'Nov. 22, 1955 2,760,161 Cutler Aug. 21, 1956 2,805,333 Waters Sept. 3, 1957 

